# Could we launch resources from the moon with electromagnetic railguns?

#### Rocky

1. Giving your someone Byzantine registration system I see why there are very few comments.
2. Crediting Gerard O'Neill with this is a little silly since everyone knows the idea had been around for years (see Robert heinlein's moon is a harsh Mistress)
3. A much simpler system is available. I don't remember who it was that did the math on this but it turns out a 50 horse electric motor and a 1 km Kevlar tether can sling a good size load (I don't remember how large) into space from the Moon with a whole lot less power and infrastructure.

#### Unclear Engineer

I am having a hard time envisioning the lunar orbit aspects of this proposal. Whatever speed the railgun can impart to a projectile, the orbit of that projectile around the Moon will be elliptical, not circular, and will intersect the lunar surface - i.e., crash back onto the surface unless there is some sort of rocket motor on the projectile that will fire at the highest point of the thrown path to raise the lowest parts of the orbit to make it roughly circular. So, a rail gun would really only be a "first stage" to any launch vehicle intended to get lunar material into lunar orbit.

I suppose that it is theoretically possible to throw a motorless projectile directly into the path of a satellite that is already in orbit around the Moon, and have that satellite "catch" the projectile. But, in reality, that is a substantial crash between the faster moving satellite and the slower moving rail gun projectile (at the point of coincident orbits). And then the orbiting satellite would need to use a rocket motor (and fuel) to reestablish its orbital speed, because picking up the slower mass would necessarily decrease the satellite's speed and cause it to go into an eliptical orbit that would have its low point closer to the lunar surface (if not under it).

#### bigpaise

This story reminds me of a novel by James P. Hogan, "The Two Faces of Tomorrow". It involves a mix of the rail gun / lunar mining system and AI. The whole plot would make an interesting movie, a thought which I've always had but it would still be relevant for today's world.

#### Gill Wright

1. Giving your someone Byzantine registration system I see why there are very few comments.
2. Crediting Gerard O'Neill with this is a little silly since everyone knows the idea had been around for years (see Robert heinlein's moon is a harsh Mistress)
3. A much simpler system is available. I don't remember who it was that did the math on this but it turns out a 50 horse electric motor and a 1 km Kevlar tether can sling a good size load (I don't remember how large) into space from the Moon with a whole lot less power and infrastructure.
Given what Heinlein wrote in 1965 "The Moon is a Harsh Mistress" the articulation of lunar mass launch was well crafted nearly 60 years ago, as Rocky so aptly pointed out. The book is a very interesting read of how the Loonies were living in 2074 to 2076. The technologies Heinlein project are very reachable with what we now know. I do not think we will go down the 'penal colony' pathway he envisioned, and wrapped a story around. I think humanity will be a bit smarter than the social constructs of the early 1960's, as we begin to develop the ARTEMIS infrastructure in the 21st century.

The technologies of Lunar mass launch are well under development. All you need to do is look at the following 3 technologies currently in terrestrial enterprises:

1. HYPERLOOP: a means of maglev transport in a 'vacuum tube' here on Earth
2. The Boring Company: a means to cost effectively drill horizontal tunnels on Earth, or Lunar regolith.
3. SpaceX Starship: a means to eventually transport mass, like a horizontal boring machine to the lunar surface.

With a Boring machine on the Lunar surface, likely the South Pole, the regolith can be extracted for mineral and water content to process into materials for lunar construction. Plus sub-surface tubes, and eventually larger caverns will provide necessary radiation protection for sustained human presence in the Lunar habitation structures. It will take time to further develop these into a viable lunar infrastructure, but the technologies are well understood.

Given that Elon Muck and Jeff Bezos both read Robert Heinlein and O'Neil, in their formative years, it seems to me that they are developing the industrial means to implement such a Lunar infrastructure in the coming decade, or so.

Time will tell..

Frankly, I think the space industry has a sound handle far beyond the application of a Naval catapult.

#### Cycappy

Also visit SpinLaunch. This seems to me as the most viable alternative with small form factor, repeatable launching, and sizeable payloads. They've already achieved 1600 km/h in early tests, and target 5 times that.

We have this capability. My question is whether this too will weaponize. As the Harsh Mistress shows, thousandths of. small but significant sized projectiles could simultaneously strike any number of locations with huge energy releases rivaling tactical nukes down this big gravity well. It would be easy, accurate and cheap. As a first strike weapon this is scary. Launching from the far side of the moon, these small payloads would be hard to detect.

Let's hope some dictator doesn't make us into a planet of apes.

#### Unclear Engineer

Fiction writers dream up all sorts of things and use incorrect or half-truth physics to "sell" their stories to the uneducated (in hard sciences) public. So, just because somebody wrote about it decades ago does not mean that it will even work according to the laws of physics, much less that some engineering is being done to make use of it, today.

Nobody has answered the orbital dynamics question in my post #3. Without some solution to that basic physics problem, throwing things into orbit from the ground is a non-starter.

#### Cycappy

Enough velocity and the right vectoring and the object will proceed into Earth's gravity well, and it's a N-body problem anyway, not just the Moon and object.

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#### Unclear Engineer

The article speaks about "One application for mass drivers was launching moon-derived materials into lunar orbit for in-space manufacturing," and "The lickety-split speed required to hurl pound-class payloads from lunar terrain into a low circular orbit around the moon is 3,758 miles per hour (1.68 kilometers per second). " [emphasis added by me].

That is just a 2-body orbital mechanics problem, and it won't work. The objects launched that way will end up crashing back on the Moon's surface. To get them into a circular orbit, some impulse must be supplied at the high point of the "throw" trajectory.

Throwing stuff from the Moon to the Earth is theoretically possible, it simply needs to be accelerated to the lunar escape velocity in a direction headed toward Earth. As a way of bombarding Earth, that would work, theoretically. But, if the idea is to get the material into a stable orbit around Earth, then again, it will require some orbital changes when near Earth. It could dip into Earth's atmosphere and "skip out" into a lower velocity, but its low point in orbit around the Earth would then still be in the upper atmosphere, and the orbit would continue to decay until it resulted in terminal reentry, unless there is some rocket used to raise the perigee (low point of Earth orbit).

I suppose there might be some 3-body solution that would put the material into an orbit that is rather high from both the Earth and the Moon that would allow for a low-energy "capture" by a 4th body that was some sort of manufacturing plant, but that would be hard to compute and not a very convenient location for something that was intended to be used on Earth. Maybe if we ever get to building things in space to continue using in space. But, maybe not. Show me the orbit if you want me to believe that this is "the future".

#### Cycappy

The article speaks about "One application for mass drivers was launching moon-derived materials into lunar orbit for in-space manufacturing," and "The lickety-split speed required to hurl pound-class payloads from lunar terrain into a low circular orbit around the moon is 3,758 miles per hour (1.68 kilometers per second). " [emphasis added by me].

That is just a 2-body orbital mechanics problem, and it won't work. The objects launched that way will end up crashing back on the Moon's surface. To get them into a circular orbit, some impulse must be supplied at the high point of the "throw" trajectory.

Throwing stuff from the Moon to the Earth is theoretically possible, it simply needs to be accelerated to the lunar escape velocity in a direction headed toward Earth. As a way of bombarding Earth, that would work, theoretically. But, if the idea is to get the material into a stable orbit around Earth, then again, it will require some orbital changes when near Earth. It could dip into Earth's atmosphere and "skip out" into a lower velocity, but its low point in orbit around the Earth would then still be in the upper atmosphere, and the orbit would continue to decay until it resulted in terminal reentry, unless there is some rocket used to raise the perigee (low point of Earth orbit).

I suppose there might be some 3-body solution that would put the material into an orbit that is rather high from both the Earth and the Moon that would allow for a low-energy "capture" by a 4th body that was some sort of manufacturing plant, but that would be hard to compute and not a very convenient location for something that was intended to be used on Earth. Maybe if we ever get to building things in space to continue using in space. But, maybe not. Show me the orbit if you want me to believe that this is "the future".
I see your point. I was thinking to supply Earth or an earth orbital station with material. Also note there would need to be a Moon orbital station for manufacturing, so an intercept could negate the need for thrusters. Possibly the intercept would also provide delta momentum for the orbital station keeping. Lots of computations sure, and fascinating. To me it's possible and just a matter of money-time.
Also, Harsh Mistress did account for thrust corrections needed for shipping grain back to earth. If you haven't read that yet and like hard sci-fi, it's a good read, though characters are simple.

#### Classical Motion

If we could convert spin into directional thrust we could do it. Launch a spinning mass and at the right time convert that spin into thrust.

Spin, potential thrust. Stored motion. Stored acceleration.

#### Unclear Engineer

If you look a the drawing of a circle and any ellipse you can make with one of its two focal points in the same place as the center of the circle, you will see that there is nowhere that an ellipse (other than the same circle, which is a special case of an ellipse) has the same position, the same direction, and the same curvature. So, at any interception of an object in a circular orbit with an object in an elliptical orbit, there will be a difference in the velocity vector, at least its magnitude, and usually also its direction. That is the place where an impulse from a rocket motor is required to make the thrown projectile match the speed and direction of the orbiting satellite.

Even if the satellite in the circular orbit is just hit with the thrown projectile, so that it "catches" it, the effect would be to knock the satellite out of its circular orbit. So, that would require a corrective impulse from a rocket motor to restore the satellite to its circular orbit.

It doesn't matter how you aim the throw, you simply cannot avoid needing propellant to get the thrown object into a circular orbit. It is basic physics.

#### ChrisA

So there is a manned space station in Lunar orbit and they have a broken pump and their toilet stops working, So "no problem" we simply launch a few kilos of dirt and rock from the Moon and they use that to fix the broken pump.

Obviously, the problem is not launching, but having some usable object to launch. No one needs tons of dirt and rock, you have to first process the rocks to metal and then machine the desired parts and combine them with electronics and apply paint and package so it can survive the extreme g-force of the rail gun. In short, you'd need an extensive supply chain on the moon to build cargo that is worth the effort to launch.

Or you put the industrial supply chain in orbit and launch raw metal ore to space. Given the huge forces applied by the rail gun, it might be that only raw ore or water ice can survive the launch.

Water ice might be the only usable product that is launch able by a gun.

The people at SpaceX have another idea -- make launching from Earth so cheap that no one would bother with lunar railguns.

#### ChrisA

It doesn't matter how you aim the throw, you simply cannot avoid needing propellant to get the thrown object into a circular orbit. It is basic physics.
I think it might be even worse. What if you launch a payload and the payload's rocket fails to fire? I think(?) the payload will impact the launcher at orbital speed. On the other hand, the moon is not a geometrical point and there are gravitational anomalies so the payload would likely miss. Even if a self-destruct where installed the result of a failed rocket might be worse if debris lands over a wide area around the launcher.

#### ChrisA

Nobody has answered the orbital dynamics question in my post #3. Without some solution to that basic physics problem, throwing things into orbit from the ground is a non-starter.
I think it is obvious that you need to put a rocket engine on the payload. You need a much smaller rocket to make the orbit circular than you to to launch from the surface. So we might think of the rail-gun as a "first stage" --- But now you have the problem of how to return the payload canister and the rocket to the lunar surface. How to slow the vehicle to zero for a soft landing? Maybe the rocket is sized to soft land the empty canister. Like a SpaceX Falcoln9. It does not take much fuel to soft-land an empty can on the Moon.

The bigger question is why send humans to space, except for tourism? In 50 years robots will be much more capable than humans and they will be happy "living" in a vacuum with no food. If not in 50 then in 100 years. The labor needs in space will over time fall to zero, except for tour guides. The Moon will be a very fun destination for the ultra-rich.

#### billslugg

I agree, there is no reason for humans in deep space. In LEO and on the Moon, yes, but long term travel outside very thick radiation shields is not a good idea. Also, there is little money to be made in deep space. Mining metals maybe.

#### Unclear Engineer

Maybe is Psyche turns out to be a rubble pile of gold, platinum and iridium nuggets waiting to be scooped up, it would be worth mining it to bring the materials back to Earth.

But, otherwise, I see human travel to other solar bodies as science missions, rather than industrial, or even tourists beyond the Moon.

I am not so enamored with robotics that I think we will be satisfied with them for trips as close as Mars. We have too many scientific questions and robots are still turning out to be too limited by assumptions in the mission designs and the idea that they should be cheaper than sending humans.

If Musk does complete his goal of putting together the launch infrastructure to colonize Mars, I am sure that NASA or somebody else will pay to use it for science missions, even if there are no takers on becoming permanent residents or even tourists.

#### ChrisA

Maybe is Psyche turns out to be a rubble pile of gold, platinum and iridium nuggets waiting to be scooped up, it would be worth mining it to bring the materials back to Earth.
For the foreseeable future, even if there were gold bars on Mars, stacked on forklift pallets, it would not make economic sense to go there (even with robots) to fetch the gold. Gold is only worth about \$1000 per once.

But, otherwise, I see human travel to other solar bodies as science missions, rather than industrial, or even tourists beyond the Moon.

I am not so enamored with robotics that I think we will be satisfied with them for trips as close as Mars. We have too many scientific questions and robots are still turning out to be too limited by assumptions in the mission designs and the idea that they should be cheaper than sending humans.
This is true today. Will it still be true in 40 years? What about in 100 years? The time span when humans can outperform robots is coming to an end, Maybe by the end of this century.
If Musk does complete his goal of putting together the launch infrastructure to colonize Mars, I am sure that NASA or somebody else will pay to use it for science missions, even if there are no takers on becoming permanent residents or even tourists.
People will go where the high paying jobs are, or will not go if there are none. Musk's biggest problem is economics, not technology. He will likey have the technology worked out by the 2050s but how will these colonists pay for the food, water, and air? No government will pay for hundreds or thousands of people to live on Mars for the rest of their lives and their grandchildren's and lives and so on forever and Musk can't come close to paying. He is not THAT rich. He has no economic plan. But at least his time line is becoming more real, I heard him say recently (I hope in my lifetime...). He is in his 50s so now it seems he is thinking 2050s for sending people.

About robots. Musk needs to build out a fuel plant and tank farm on Mars and a parts depot and he needs to test it all BEFORE the first crew lands. He will need a real launch pad built before he can do a return trip. I think the only way is to use some very advanced robots.

#### Unclear Engineer

Robots will continue to improve with respect to doing things.

It remains to be seen how much they can be improved with respect to their ability to discover things that are unexpected.

#### ChrisA

Robots will continue to improve with respect to doing things.

It remains to be seen how much they can be improved with respect to their ability to discover things that are unexpected.
The robot never works be itself. An example of a robt "discovering" something in space is the rovers on Mars. The robot does the work on Mars and every moring real humans meet in a conference room at JPL to discus the latest results and plan the next day's activity. Then later someone assembles the commands to be sent to Mars. Yes this process is slow but much has been discovered on mars

As the robot has become more sophisticaed it is given a longer set of higher level instuctions. For example they used to tell the rover how to move the wheels, not they only give it a point to drive to.

A much more sophisticated robot would be given even higher level instructions like "if you see rock type X, take a sample, but if type y or z take a spectrum and we will look at it and say if we want a sample.

This will improve untill we can talk to it almost as if it were human. ChatGPT is good at language already but this is just the very beginning, it will mature over the comming decades

At some point we will have domestic robots that can do tasks like cleaning a batchroom and folding laudry and crearing dishs after dinner or bringing an Amazon package in from ther front porch. This kind of robot could do a lot in space, but evcen that is just the beginning. decade by decade we will see improvements

But already we have discovered much about the solar system, but was any of this done by astronauts? That said, it is still fun to go places or even to hear descriptions and see videos made by others. We send people for that reason.

#### Unclear Engineer

Well, there is still this:

https://daily.jstor.org/we-might-have-accidentally-killed-the-only-life-we-ever-found-on-mars/ .

What we need is some(body/thing) that can do critical thinking, based on broad knowledge.

At this point, ChatGPT is only a mimic of what it thinks people will do. And, it makes things up, and lies about references to support what it makes up. Not something I would trust.

Yes, it will get better, and there are already purpose-built AIs that are better (at specific tasks).

Someday (maybe soon), somebody may fake a video of a trip to Mars. IF the AI used got its "education" from television, it will probably involve Klingons, Darth Vader and superluminal speeds.

#### Classical Motion

It will become a Hollywood and political script very quickly.

#### Bill Sticker

Electromagnetic launches of material from the lunar surface can be more efficient than conventional rocket launches that rely on chemical fuels sent from Earth. But are they feasible?

Could we launch resources from the moon with electromagnetic railguns? : Read more
I point you Prof Eric Laithwaite who was the Grandaddy of these type of electromagnets, suggest you watch this from way back when:

Seems to me as usual you ain't looking at the past properly.

#### Unclear Engineer

I watched the video, but there was no sound. So, all I saw was a metal plate moving back and forth over a series of magnetic coils. Nothing new to me there. Was there something said in the audio that is important? Please provide your point in text.

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